WindowsServer2003-KB3067903-x64-ENU appears in the XP64 update list.
It's install log says: "CheckSystem: GetMachineType failed :STATUS_PLATFORM_MISMATCH".https://support.microsoft.com/en-us/kb/3067903 says it is for "all supported x64-based versions of Windows Server 2003".
There is no mention of it being used for XP64.